Integrated Moisture Index
Integrated Moisture Index
In a mesophication context, oaks might have a competitive advantage over competitors such as red maple when long-term soil moisture is limited (Loftis and McGee 1993). With this in mind, Iverson et al. (1996; also see Iverson et al. 1997) developed the Integrated Moisture Index (IMI), a GIS tool that uses readily available input datasets (e.g., a Digital Elevation Model, DEM) to generate a single number that ranges from 0-100 that captures where soil moisture should be higher:
- where solar radiation is minimized
- where flow accumulation occurs (lower positions on slopes)
- and in soils with higher water storage capacity
Raster map of the Integrated Moisture Index
Using updated methods kindly shared by Matt Peters (in review, 2025), I calculated the IMI and map the raw data below. For both the raster and the HUC 12 maps, lower values are hypothesized to be better for oaks.
Mean Integrated Moisture Index per HUC 12
The map below depicts mean IMI values per HUC 12 watershed as calculated using Zonal Statistics in ArcGIS Pro.